[Xymon] Xymon client on MacOS Catalina (10.15)

[Mark Wagner]

On Sat, 5 Sep 2020 13:29:54 +1000
Brian Scott <Brian.Scott at bunyatech.com.au> wrote:

> Hi list,
> 
> Has anyone had experience with running the xymon client on the latest
> Macos?
> 
> My particular problem is that the handling of disk mounts and
> capacities has gone seriously weird. First exhibit - output from the
> mount command:
> 
> # mount
> /dev/disk1s1 on / (apfs, local, read-only, journaled)
> devfs on /dev (devfs, local, nobrowse)
> /dev/disk1s2 on /System/Volumes/Data (apfs, local, journaled,
> nobrowse) /dev/disk1s5 on /private/var/vm (apfs, local, journaled,
> nobrowse) map auto_home on /System/Volumes/Data/home (autofs,
> automounted, nobrowse)
> 
> All volumes are either marked nobrowse or read-only so no disks are
> selected by xymonclient-darwin.sh. This has the immediate kick on
> effect of causing a bash set command to dump all set variables
> because the filesystem list is empty. Ignoring this because we
> actually want to select some filesystems, the question is which ones.
> Looking at the output from df:
> 
> # df -P -H
> Filesystem      Size   Used  Avail Capacity  Mounted on
> /dev/disk1s1    1.0T    11G    92G    11%    /
> devfs           345k   345k     0B   100%    /dev
> /dev/disk1s2    1.0T   893G    92G    91%    /System/Volumes/Data
> /dev/disk1s5    1.0T   3.2G    92G     4%    /private/var/vm
> map auto_home     0B     0B     0B   100%    /System/Volumes/Data/home
> 
> It looks like /dev/disk1s1, s2 and s5 are all the same real partition
> but account for different space from it, i.e. total size = 1.0T, Used
> = 11G+893G+3.2G=907.2G, Avail=92G.
> 
> This would suggest that a reasonable thing to monitor would be one of
> these entries ('/' makes some sense) and derive used as size-avail
> (1.0T-92G).

APFS volumes are more akin to BTRFS subvolumes or ZFS filesystems
than to traditional partitions: the available space on the physical
storage is shared between them on an as-needed basis.

There might be some Apple-specific command line tool to get the
statistics you want, but failing that, you'll need to track which
partitions are APFS versus something else when deciding how to
calculate usage.

-- 
Mark